from TurtleWorld import *

world = TurtleWorld()

#print bob
#for i in range(4):
#    fd(bob, 100)
#    lt(bob)
#wait_for_user()

def square(t,length):
    for i in range(4):
        fd(t, length)
        lt(t)

def polygon(t,length,n):
    for i in range(n):
        fd(t, length)
        lt(t,360/n)

def polyline(t, n, length, angle):
    """Draw n line segments with the given length and
    angle (in degrees) between them.
    """
    for i in range(n):
        fd(t, length)
        lt(t, angle)

def arc(t, r, angle):
    arc_length = 2 * math.pi * r * abs(angle) / 360
    n = int(arc_length / 4) + 1
    step_length = arc_length / n
    step_angle = float(angle) / n

    # making a slight left turn before the polyline reduces
    # the error caused by the linear approximation of the arc
    lt(t, step_angle/2)
    polyline(t, n, step_length, step_angle)
    rt(t, step_angle/2)

def circle(t, r):
    arc(t, r, 360)

def draw_bob():
    bob = Turtle()
    bob.delay = 0.00001
    #square(bob,70)
    #polygon(bob,75,7)
    for i in range(30,100):
        circle(bob,i)
    
    
draw_bob()